Salt bath furnace



March 15, '1949'. A. F. HOLDEN SALT BATH FURNAGE Filed April 5, 1945/ffegas F Ha/a'eh 2 Sheets-Sheet 1 INVENTOR .f ATTORNEY5 Maich l5, 1949.A. F. HOLDEN SALT BATH FURNACE 4 2 Sheets-Sheet, 2

Filed April 5, 1945 M d .w 4 MH M s E o VCI m. MM Wm L m l f mm PatentedMar. l5, 1949 UNITED STATES YPATENT OFFICE SALT BATH FURNACE Artemas F.Holden, New Haven, Conn.

Application April 5, 1945, Serial No. 586,649

The present invention comprises an improvement in salt bath furnaces ofthe character commonly used in heat treating of metals and whichcomprise a heat-insulated shell which supports and surrounds the sidewalls and bottom of a metal pot formed of suitable alloy to containmlten salts at temperatures ranging up to 2250 F.

As the work, which is heat-treated in the molten salts within the 'potAis lifted from the pot, a small amount of the liquid salts will bedripped over the edge of the pot. These salts, in furnaces of the oldwell-known construction, tend to seep under the edge of the :pot and totravel .down-i ward on the outside of the pot between the pot and theheat-insulating material. This tends to cause erosion of the pot andthereby shortens the effective life of the pot container for the salts.The reason for this is due to the fact that heretofore in the art theupper portion of the pot is heated whereby the molten salts retain theirfluidity and thus may escape beneath the rim of the pot, as specified.

The present invention overcomes the defects of the known prior art byproviding a cooling area adjacent the mouth of the pot whereby any saltsdripped over the edge of the pot are frozen, and thus their fluidity isdestroyed and the seepage of the salt materials over the outside of thepot and between the pot and the heat-insulation is prevented. Thepreferred cooling arrangement comprises a hollow metal ring upon whichthe rim of the pot rests and through which hollow ring a cooling medium,such as air, water, steam, or other cooling medium, is circulated. Thecoolingmedium carries away the heat from the upper.

end of the pot and cools the same. Where air is used, the passage of theair through the hollow ring heats the air, and in a gas-red pot this airmay be conducted to the gas burner, thereby sulpplying heatedair to theburner and consequently rendering the burner more eilicient in theheating of the pot.

Other and further objects of the present invention will in part beobvious and will in part be pointed out hereinafter in the descriptivematter following.

It is to be understood that the disclosure herewith is illustrative andis not to be interpreted in a limiting sense.

Fig. 1 is an illustration of a gas-red lfurnace in which the presentinvention is incorporated and wherein a portion of the furnace is shownin section.

Fig. 2 is a plan sectional view of the cooling ring taken onsubstantially line 2--2 of Fig. l and showing the ring detached from thefurnace.

Fig. 3 is an elevational sectional View of the detail of the coolingring taken substantially on y line 3-3 of Fig. 2 adjacent the partitionin the ring.

Fig. 4 is a detail section illustrating thevmounting of a pot in thefurnace adapted to be heated electrically and showing fire-proofingmaterial substantially in contact with the pot.

Referring now more especially to Fig. 1 of the drawings whichillustrates a gas-'red furnace in accordance with the present invention,a casing I supports heat-insulating material 2, which in a gas-firedfurnace is spaced from the side walls ci a pot of suitable alloy metalin such manner as to tpovide a flame chamber 5 surrounding the po Amelted salt bath 6 is contained Within the pot i and is the medium inwhich metallurgical articles are submerged for heat treatment. A burner'I of the gas and air or oil and air type is mounted on the side of thecasing i and a name opening 8 leads into the ilarne chamber The pot issupported upon a cooling member comprising a base plate 9, side wallslil and Il, and a top wall I2. These parts may be made of suitable metaland welded together to form a space I4. An inlet pipe I5 leads into thespace I4 and an outlet pipe I6.

leads away from the hollow space. A partition Il, see Figs. 2 and 3, isprovided between the inlet pipe I5 and the outlet pipe ISso thatthe-cooling medium is compelled to flow the ull length of the hollowspace I4 before it reaches the outlet pipe. The upper end of the pot Ilis provided with a ilange I 8 which rests upon the top wall I2 of thecooling member and the base plate 9 restson heat-insulating materialwhich surrounds the pot. Where air is used as the cooling medium, theair outlet pipe I 6 leads through a controlvalve I9 to the burner 'Iwhich is supplied by gas or oil through the pipe 20 leading to theburner 'I so that when the furnace is operating, the air circulatingthrough the hollow space I4 becomes heated as it takes away the heatfrom the upper end of the pot and this heated Iair comprises the airsupply to the burner I so that the burner operates more eiliciently thanwhen cold air is drawn in directly from atmosphere. There may beconditions where it is desirable to divert a portion or all of theheated air away from the burner 1, and to this end an outlet pipe 24 isprovided adjacent to the valve I9, which valve is so constructed as todeliver the heated air proportionally through the pipe I 6 to the burner'l and through the outlet pipe 24, or all the heated air either to theburner 7, or to the outlet pipe 24. Another valve 25 is provided topermit air to be supplied to the burner 7, when the heated air is cutoff from the burner 1. These valves I9 and 25 may be operated in anymanner well-known in the art.

Surrounding the upper end of the pot with a cool surface causes anysalts which may be spilled over the edge or flange of the pot to fall onthis surface and to be congealed and hardened so that this waste saltloses its fluidity and does not tend to iiow or creep down the outsideof the pot.

Referring now to Fig. 2, it will be noted that the space I4 isinterrupted by baiiles 2| which cause the cooling medium, such ascompressed air, to take a tortuous path and thereby cause a turbulentcirculation of the cooling medium which absorbs heat from the inner sidewall I and from the upper end of the pot, thereby cooling the same forthe purpose specified.r The baffles 2| and the partition Il extend fromthe base plate 9 to the top wall l2 in order to reinforce the top walland prevent the crushing of the cooling member due to the weight of thepot 4 when filled with the salt bath 6, which weight is augmented by theweight of metal objects in the bath undergoing treatment.

Fig, 3 illustrates the inlet pipe I5 and the outlet pipe l5 leadingthrough the top wall l2 on each side of the partition l1, and where acooling medium other than compressed air is used the outlet pipe I6leads to a proper disposal means for the outlet cooling medium and inthis case the outlet is not connected with the burner '1.

Fig. 4 is a detail view showing a portion of the side wall of thefurnace adjacent the pot in seotion and illustrates an electricallyheated furnace in which electrodes 22 extend into the salt bath B andpassage of the current from the electrodes through the salt heats thebath. In an electrical furnace there is no necessity for a flame chamberaround the pot, and, therefore, the heat-insulation is in substantialcontact with the side walls of the pot. This produces a condition whereseepage of salts may interlock the pot and the heat-insulating material.Under these conditions, severe erosion may occur to the alloy metal pot,and the present invention, therefore, overcomes a decided disadvantageof the known prior art.

The present invention is illustrated as used with a pot which iscircular in horizontal crosssection, but since the invention is notconcerned with the shape of the salt container, it is equally adapted topots having shapes in horizontal crosssection other than circular andthe invention tending within said heat insulation, a hollow coolingmember surrounding the upper end of and supporting said pot and adaptedto form a conduit through which a cooling fluid may be circulated tocool the upper end of said pot and prevent creepage of salt around theexterior of said pot, and baffles within said hollow cooling member tocause the cooling medium to take a tortuous path through said hollowcooling member, and reinforce said member against crushing.

2. In a salt bath furnace, a shell.' heat insulation Within said shell,a. salt bath metallic pot extending within said heat insulation, ahollow cooling member surrounding the upper end of and supporting saidpot and adapted to form a conduit through which a cooling fluid may becirculated to cool the upper end of said pot and prevent creepage ofsalt around the exterior of said pot, and baffles within said hollowcooling member extending from the bottom to the top wall thereof toreinforce said member against crushing and cause the cooling medium totake a tortuous path through said member.

3. In a salt bath furnace, a furnace shell, heat insulation within andsupported by the shell, a

salt bath container mounted within said heat in-V tainer, and an annularcooling ring for supporting and cooling the rim of the container, saidcooling ring having a passage for conducting a cooling fluidtherethrough, having an extended horizontal base supported by said heatinsulation, having a horizontal upper containerrim supporting surfaceand having a circumferential inner marginal flange projecting above the'container-rim supporting surface and between the container-rim and thecontainer.

ARTEMAS F. HOLDEN.

REFERENCES CITED The following references areof record in the file ofthis patent:

UNITED STATES PATENTS` Number Name Date 1,539,924 Waite June 2, 19251,705,714 Carpenter Mar. 19, 1929

